CN116125629A

CN116125629A - Optical imaging system and camera lens

Info

Publication number: CN116125629A
Application number: CN202211623039.XA
Authority: CN
Inventors: 侯昌伦
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-12-16
Filing date: 2022-12-16
Publication date: 2023-05-16

Abstract

The invention discloses an optical imaging system and a camera lens, wherein the optical imaging system comprises a plurality of optical elements arranged along an optical path, and all surfaces of the optical elements at least comprise two surface types of free-form surfaces, diffraction microstructure surfaces and super-surfaces; wherein when the diffraction microstructure faces are included, the diffraction microstructure faces are arranged in pairs. The optical imaging system is applied to the photographic lens, can meet different full-field angles, and has higher imaging quality and compact structure on the basis of reducing the number of lenses.

Description

Optical imaging system and camera lens

Technical Field

The present invention relates to the field of optical imaging devices, and in particular, to an optical imaging system and an imaging lens.

Background

With the popularity of mobile electronic devices, related technologies of camera modules for helping users acquire images (e.g., video or images) applied to mobile electronic devices have been rapidly developed and advanced, and in recent years, camera modules have been widely used in various fields such as medical treatment, security, industrial production, etc.

In order to meet the increasingly wide market demands, high-pixel, small-size and large-aperture imaging modules are irreversible development trends. The Chinese patent document with publication number CN113703135A discloses a high-pixel large-target-surface large-aperture wide-angle front-view optical system and an imaging module applied by the same; chinese patent publication No. CN109507784a discloses a high-pixel large-aperture-depth imaging optical system and an image pickup module using the same.

However, a large aperture, a high pixel (larger area image sensor), and a large field of view cause problems in that the total optical length of the lens becomes long, the optical system structure is more complicated, and aberration correction is more difficult.

In recent years, with rapid development of optical element processing technology, high-precision complex optical surface processing technology is becoming mature. The processing technologies such as high-precision single-point diamond lathe precision die processing, high-precision injection molding technology and the like are utilized, so that mass production of high-precision complex surfaces can be realized. The complex optical surface is used in the field of small-size optical devices (such as the fields of mobile phone camera modules, endoscopic imaging systems and the like), and is beneficial to reducing the distortion of a large field angle and reducing the total optical length of the camera modules to a certain extent.

Disclosure of Invention

The invention provides an optical imaging system and an imaging lens, which have higher imaging quality and a compact structure on the basis of reducing the number of lenses.

An optical imaging system comprising a plurality of optical elements arranged along an optical path, all surfaces of the plurality of optical elements comprising at least two of a freeform surface, a diffractive microstructure surface and a super-surface; wherein when the diffraction microstructure faces are included, the diffraction microstructure faces are arranged in pairs.

In the invention, the free curved surface is a continuous smooth curved surface symmetrical about the XY two directions, and the surface of the optical element is arranged into a diffraction microstructure surface or a super surface to be used as a diffraction optical element.

Further, the equation of the free-form surface is:

wherein: z (x, y) is the optical surface elevation; k is a conic coefficient; c is the radius of curvature; r is the radial height in the direction of the optical axis, r ² ＝x ² +y ² ；A _i Is a polynomial coefficient, E _i (x, y) is a polynomial.

Further, the free-form surface is of a double-symmetrical structure, and the polynomial E _i The odd-order term coefficients of x and y in (x, y) are 0, specifically as follows:

wherein A is _i Is a polynomial coefficient.

When diffraction microstructure surfaces are included, two layers of diffraction microstructure surfaces are arranged on a plane, spherical, aspherical or free-form surface substrate of an optical element with different refractive index materials in each pair of diffraction microstructure surfaces, and a gap between the two layers of diffraction microstructure surfaces is air or other light-transmitting filling medium.

The interval delta between the two layers of diffraction microstructure surfaces is 1-20 um, and the phase distribution of the diffraction microstructure surfaces is respectively

And->

Z _A (ρ)、Z _B (ρ) is the microstructure morphology of the two layers of diffraction microstructure surfaces, n _A (lambda) and n _B (lambda) is the refractive index of the two-material optical element; the heights of the two layers of diffraction microstructure surfaces are H respectively ₁ And H ₂ The phase height distribution function of the diffractive microstructure surface satisfies the following condition:

wherein lambda is ₀₁ 、λ ₀₂ To design wavelength, n _A (λ ₀₁ )、n _A (λ ₀₂ ) And n _B (λ ₀₁ )、n _B (λ ₀₂ ) For the design wavelength lambda ₀₁ 、λ ₀₂ Two corresponding refractive indices on the two-material optical element.

The diffraction microstructure surface is a blazed binary optical microstructure, and specifically comprises: processing a ridged cylindrical diffraction microstructure optical surface with the size smaller than the micro nano size of wavelength on a substrate by adopting photoetching and etching processes, wherein the equivalent refractive index dispersion relation of the diffraction microstructure meets the following relation:

wherein n (f, lambda) _∞ ) Is the equivalent refractive index at the static limit; q (f, epsilon) is an expression related to a filling factor f and a dielectric constant epsilon of the material, lambda is a period of the sub-wavelength structure, and lambda is the wavelength of the incident light wave;

wherein d is the diameter of the microstructure cylinder or the width of the ridge; and satisfies f, Λ > δt, (1-f), Λ > δt; wherein δt is the finest processed line width; equivalent refractive index is n _eff (f ₁ ，λ ₀ ) And n _eff (f ₂ ，λ ₀ ) I.e. the filling factor of the microstructure is between f ₁ And f ₂ Between them; the etching depth h satisfies:

at the design wavelength lambda ₀ When the microstructure equivalent bit distribution at different filling factors is as follows:

phase transfer function

And->

The relation between the two is:

the super surface is an artificial two-dimensional material which is arranged on a plane or curved surface substrate and takes a nano-scale elliptic cylinder, a cuboid or an irregular graph as a basic unit, and comprises a transmission type or reflection type super surface.

By utilizing the optical imaging system, the invention also designs a plurality of imaging lenses with different full field angle FOVs.

In the first type of imaging lens, the full field angle FOV of the imaging lens satisfies FOV >90 °, and the optical imaging system is adopted, wherein the optical elements included in the optical imaging system are at least three lenses; all of the surfaces of the lens include at least one free-form surface and at least one pair of diffractive microstructured surfaces or a supersurface.

As one embodiment of the first imaging lens, the optical imaging system includes, in order from an object side to an image side along an optical axis: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens;

wherein the first lens has negative focal power, the second lens has negative focal power, the third lens has positive focal power, the fourth lens has negative focal power, the fifth lens has negative focal power, and the sixth lens has positive focal power; all surfaces of the first lens to the sixth lens comprise at least one free-form surface and at least one pair of diffraction microstructure surfaces or one super-surface.

In the second type of imaging lens, the full field angle FOV of the imaging lens satisfies FOV <30 °, and the optical imaging system is adopted, wherein the optical elements included in the optical imaging system are at least one lens and at least one prism including a refractive surface and a reflective surface, and the surfaces of all lenses include at least one free-form surface and at least one pair of diffraction microstructure surfaces or one super-surface.

As an embodiment of the second imaging lens, the optical imaging system includes, in order from an object side to an image side along an optical axis, a first lens, a second prism, and a third lens;

wherein the first lens has positive optical power, the second prism has two transmission surfaces and three reflection surfaces, and the third lens has negative optical power;

the second surface of the first lens is adjacent to the first transmission surface of the second prism, the spacing distance is 1-20 um, and the surface shapes are the same; the second surface of the first lens and the first transmission surface of the second prism are diffraction microstructure surfaces; the three reflecting surfaces of the second prism are free curved surfaces;

the second reflecting surface of the second prism is arranged on the light path of the first reflecting surface of the second prism, and the third reflecting surface of the second prism is arranged on the light path of the second reflecting surface of the second prism; the center normal line of the first reflecting surface, the center normal line of the second reflecting surface and the center normal line of the third reflecting surface of the second prism are intersected.

In the third type of imaging lens, the full field angle FOV of the imaging lens satisfies the angle FOV of 30 degrees or more and 90 degrees or less, and the optical imaging system is adopted, wherein the optical elements contained in the optical imaging system are at least four lenses; all of the lens surfaces include at least two free-form surfaces and at least one pair of diffractive microstructured surfaces or a supersurface.

As one embodiment of the third imaging lens, the optical imaging system includes, in order from an object side to an image side along an optical axis, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens;

wherein the first lens has positive focal power, the second lens has negative focal power, the third lens has positive focal power, the fourth lens has focal power, the fifth lens has focal power, the sixth lens has positive focal power, the seventh lens has negative focal power, and the eighth lens has negative focal power;

all surfaces of the first lens to the eighth lens comprise at least two free curved surfaces and at least one pair of diffraction microstructure surfaces or one super surface.

Compared with the prior art, the invention has the following beneficial effects:

1. the invention uses the free-form surface optical element and the diffraction optical element to make the common automatic focusing module, which can reduce the total optical length and improve the imaging quality of the optical system. The free curved surface, the diffraction microstructure surface and the super surface can reduce or minimize the aberration of the optical system, realize the functions of correcting the aberration and reducing the distortion, and can also play the role of reducing the total optical length and/or the volume of the module.

2. The invention uses complex optical surfaces (free curved surface, diffraction microstructure surface and super surface) for the camera lens module, which is helpful for reducing distortion of large field angle and reducing optical total length of the camera module to a certain extent.

Drawings

FIG. 1 is a schematic view of an imaging structure of a free-form surface according to the present invention;

FIG. 2 is a schematic diagram of diffraction microstructure facets arranged in pairs;

FIG. 3 is an enlarged schematic view of FIG. 2;

FIG. 4 is a graph showing the morphology and phase distribution of a first diffraction microstructure;

FIG. 5 is a graph showing the morphology and phase distribution of a second diffraction microstructure;

FIG. 6 is a schematic view of the structure of a subsurface;

FIG. 7 is a schematic view of an optical imaging system with a field angle of view smaller than 30 ° according to embodiment 1;

fig. 7 (a) is an optical path diagram of the optical imaging system of embodiment 1;

FIG. 7 (b) is a graph of the modulation pass point function of the optical imaging system of example 1;

FIG. 7 (c) is a plot of field curvature and distortion of the optical imaging system of example 1;

FIG. 7 (d) is a graph showing diffraction efficiency at different wavelengths of a diffraction structure comprising two diffraction microstructure facets in the optical imaging system of example 1;

FIG. 7 (e) is an equivalent phase distribution of the first diffractive microstructure surface in the optical imaging system of example 1;

FIG. 7 (f) is a microstructure distribution of the first diffractive microstructure surface in the optical imaging system of example 1;

FIG. 7 (g) is an equivalent phase distribution of a second diffractive microstructure surface in the optical imaging system of example 1;

FIG. 7 (h) is a microstructure distribution of the second diffractive microstructure surface in the optical imaging system of example 1;

FIG. 8 is a schematic view of an optical imaging system with a field angle of view of more than 90 ° according to embodiment 2;

fig. 8 (a) is an optical path diagram of the optical imaging system of embodiment 2;

FIG. 8 (b) is a graph of the modulation pass point function of the optical imaging system of example 2;

FIG. 8 (c) is a field curvature and distortion curve of the optical imaging system of example 2;

FIG. 8 (d) is a graph showing diffraction efficiency of a diffraction structure comprising two diffraction microstructure facets in the optical imaging system of example 2 at different wavelengths;

FIG. 8 (e) is an equivalent phase distribution of the first diffractive microstructure surface in the optical imaging system of example 2;

FIG. 8 (f) is a microstructure distribution of the first diffractive microstructure surface in the optical imaging system of example 2;

FIG. 8 (g) is an equivalent phase distribution of a second diffractive microstructure surface in the optical imaging system of example 2;

FIG. 8 (h) is a microstructure distribution of the second diffractive microstructure surface in the optical imaging system of example 2;

fig. 9 is a schematic view of an optical imaging system in which the angle of view is between 30 ° and 90 ° according to embodiment 3;

fig. 9 (a) is an optical path diagram of the optical imaging system of embodiment 3;

FIG. 9 (b) is a plot of the modulation pass point function of the optical imaging system of example 3;

FIG. 9 (c) is a plot of field curvature and distortion of the optical imaging system of example 3;

FIG. 9 (d) is a graph showing diffraction efficiency at different wavelengths of a diffraction structure comprising two diffraction microstructure facets in the optical imaging system of example 3;

FIG. 9 (e) is an equivalent phase distribution of the first diffractive microstructure surface in the optical imaging system of example 3;

FIG. 9 (f) is a microstructure distribution of the first diffractive microstructure surface in the optical imaging system of example 3;

FIG. 9 (g) is an equivalent phase distribution of a second diffractive microstructure surface in the optical imaging system of example 3;

fig. 9 (h) shows the microstructure distribution of the second diffractive microstructure surface in the optical imaging system according to example 3.

Detailed Description

The invention will be described in further detail with reference to the drawings and examples, it being noted that the examples described below are intended to facilitate the understanding of the invention and are not intended to limit the invention in any way.

In the invention, the optical imaging system comprises the free-form surface element and the diffraction optical element, and the free-form surface element and the diffraction optical element are adopted, so that the optical imaging system has higher imaging quality and a compact structure on the basis of reducing the number of lenses.

The free-form surface of the free-form surface element is a continuous smooth surface symmetrical about the XY two directions, and the diffractive optical element is an optical element of at least one pair (bilayer or multilayer) of diffractive microstructure surfaces or is a super-surface diffractive optical element.

In the present invention, the equation describing the free-form surface is:

wherein z (x, y) is the optical surface elevation; k is a conic coefficient; c is the radius of curvature; r is the radial height in the direction of the optical axis; with r ² ＝x ² +y ² ；A _i Is a polynomial coefficient.

The free-form surface model is of a double symmetrical structure, and the odd-order term coefficients of x and y in the polynomial are 0.

As shown in fig. 1, an imaging structure of a free-form surface is shown, which comprises a first free-form surface 1, a second free-form surface 2 and an image sensor surface 3.

In each pair of diffractive microstructure surfaces, two diffractive microstructure surfaces are arranged on a plane, sphere, asphere or free-form surface substrate of an optical element of a different refractive index material, and a gap between the two diffractive microstructure surfaces is air or other light-transmitting filling medium.

As shown in fig. 2 and 3, a pair of (double layer) diffractive microstructure surfaces is shown, which includes a first lens 4, a second lens 5, a first lens diffractive microstructure substrate curved surface 6, a second lens diffractive microstructure substrate curved surface 7, a first lens diffractive microstructure 8, a second lens diffractive microstructure 9, and a filling medium 10. Wherein the filling medium 10 is an air space or transparent medium layer, and the refractive index of the first lens 4 is n _A The refractive index of the second lens 5 is n _B The thickness of the packing medium 10 is δ.

The microstructure morphology of the diffraction microstructure surface is Z respectively _A (ρ)、Z _B (ρ), the phase distribution of the diffraction microstructure surface is respectively

And->

Fig. 4 shows the relationship between the morphology and the phase distribution of the first diffraction microstructure, in which (a) is the shape distribution of the diffraction microstructure, (b) is the refractive index distribution of the diffraction microstructure material, and (c) is the phase distribution corresponding to the diffraction microstructure.

Fig. 5 shows the relationship between the morphology and the phase distribution of the second diffraction microstructure, in which (a) is the shape distribution of the diffraction microstructure, (b) is the refractive index distribution of the diffraction microstructure material, and (c) is the phase distribution corresponding to the diffraction microstructure.

The super surface is an artificial two-dimensional material which is arranged on a plane or curved surface substrate and takes a nano-scale elliptic cylinder, a cuboid or an irregular graph as a basic unit, and comprises a transmission type or reflection type super surface. As shown in fig. 6, (a) is a super surface formed by nanostructure distribution on a planar substrate, and (b) is a super surface formed by nanostructure distribution on a curved substrate, which includes a planar substrate 10, a nanostructure 11, and a curved substrate 12.

By utilizing the optical imaging system, the invention designs a plurality of imaging lenses with different full field angle FOVs.

Example 1

As shown in fig. 7, the optical imaging system with a full field angle FOV satisfying FOV <35 ° includes a lens 13, a prism 14, a lens 15, and an image detector 16. S1 and S2 are front and rear transmission surfaces of the lens 13, wherein S2 is a diffraction microstructure surface; s3, S4, S5, S6 and S7 are optical surfaces of the prism 14, wherein S4, S5 and S6 are free-form surface reflection surfaces, S3 is a diffraction microstructure surface and S7 is a transmission surface; s8 and S9 are front and rear transmissive surfaces of the lens 15. S2 and S3, wherein the adjacent interval range of the two diffraction microstructure surfaces is 2-20 microns, and the two diffraction microstructure surfaces have the same substrate curved surface.

FIG. 7 (a) is an optical path diagram of an optical imaging system; FIG. 7 (b) is a graph of the modulation pass point function of the optical imaging system; FIG. 7 (c) is a graph of field curvature and distortion of an optical imaging system; FIG. 7 (d) is a graph of diffraction efficiency at different wavelengths for a diffraction structure consisting of two diffractive microstructure facets in an optical imaging system; FIG. 7 (e) is an equivalent phase distribution of a first diffractive microstructure surface in an optical imaging system; FIG. 7 (f) shows the microstructure distribution of the first diffractive microstructure surface in an optical imaging system; FIG. 7 (g) is an equivalent phase distribution of a second diffractive microstructure surface in an optical imaging system; fig. 7 (h) shows the microstructure distribution of the second diffractive microstructure surface in the optical imaging system.

In this embodiment, the optical imaging system shown in fig. 7 is applied to a mobile phone built-in long focal length optical lens, the focal length is 19.2mm, the relative aperture f#2.1, the detector is a 1/2.5 "CMOS, and three free-form surface reflection surfaces and 2 diffraction microstructure diffraction surfaces are adopted. All the optical lens materials were resin materials, and the material distribution is shown in table 1 below:

TABLE 1

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The second surface of the first lens and the first surface of the second lens are diffraction microstructure surfaces, the interval between the two microstructure surfaces is 20 microns, and the microstructures of the two microstructure surfaces are distributed on an aspheric substrate. The microstructure surface phase coefficients are shown in table 2 below:

TABLE 2

Sequence number	Phase coefficient	L1S2	L2S1
				1	A ₁	-8.710E006	7.593E006
2	A ₂	-5.721E009	7.883E009
				3	A ₃	-3.715E011	-7.400E011
4	A ₄	6.433E016	-6.514E016
				5	A ₅	0	0
6	A ₆	0	0

Note that: the normalized radius corresponding to the phase coefficient is 1.0mm.

The diffractive microstructure substrate is aspherical and the corresponding aspherical coefficients are shown in table 3 below:

TABLE 3 Table 3

Sequence number	Aspheric coefficient	L4S2	L5S1
					1	ɑ ₁	0.0	0.0
2	ɑ ₂	0.0019045101	0.0019045101
				3	ɑ ₃	0.0075311795	0.0075311795
4	ɑ ₄	-0.0028755655	-0.0028755655
				5	ɑ ₅	0.00048739694	0.00048739694
6	ɑ ₆	0.00014100397	0.00014100397
				7	ɑ ₇	-8.3505669E-005	-8.3505669E-005
8	ɑ ₈	1.5847911E-005	1.5847911E-005

The front and back surfaces of the second lens are free-form surfaces, and the free-form surface coefficients are shown in the following table 4:

TABLE 4 Table 4

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Note that: the normalized radius is 2.052mm.

The height of the surface microstructure of the first diffractive optical element is H ₁ The second diffraction element has a surface microstructure of height H = 8.223 μm ₂ = 10.751 μm; the diffraction microstructure surface has 56 zones in total, and the narrowest zone width is 53.56um (as shown in fig. 7 (f)); the diffraction microstructure surface II has 60 zones, and the narrowest zone width is 39.21um (as shown in (h) of fig. 7);

as can be seen from fig. 7 (d), a diffraction efficiency that remains high over a very wide band can be obtained with a double layer diffraction element. While single-layer diffraction elements only glint precisely at the design wavelength (diffraction efficiency 100%), the diffraction efficiency drops very much in the short-and long-wave portions that deviate from the design wavelengthFast. It can also be seen from the above calculation that the depth of the microstructure is greatly increased after diffraction using the double layer microstructure relative to the single layer microstructure (H ₁ ＝23.2μm，H ₂ =16.8 μm, and in the case of a single layer diffraction structure, the depth of the microstructure is about 1 μm). The depth value is greater if the microstructure is in the mid-wave infrared or long-wave infrared. H ₁ 、H ₂ The value of (2) depends on the dispersion characteristics of the two materials and the two design wavelengths chosen. Considering the limitation of the practical processing technology, the aspect ratio of the microstructure which can be processed by the existing ICP equipment is 7-8, and the finer line width is larger as the depth of the microstructure is larger.

The manufacturing of the multi-layer binary diffraction optical element is similar to that of the single-layer diffraction optical element, in addition to etching depth errors, line width errors and alignment errors caused by multiple overlay, lateral alignment errors, stacking inclination errors and the like among the diffraction microstructures of each layer can reduce the diffraction efficiency of the element, and the performance of the multi-layer binary optical element is affected.

Example 2

As shown in fig. 8, the optical imaging system satisfying the full field angle FOV of more than 90 ° includes a lens 17, a lens 18, a lens 19, a lens 20, a lens 21, a lens 22, and an image detector 23, with a diaphragm between the lens 18 and the lens 19. P1 to P12 are all transmissive surfaces, wherein the second surface P8 of the lens 20 and the first surface P9 of the lens 21 are diffraction microstructure surfaces, and the adjacent interval range of the two diffraction microstructure surfaces P8 and P9 is 2-20 micrometers, and the two diffraction microstructure surfaces have the same substrate curved surface. The front and rear surfaces P11, P12 of the lens 22 are free curved surfaces.

FIG. 8 (a) is an optical path diagram of an optical imaging system; FIG. 8 (b) is a graph of the modulation pass point function of the optical imaging system; FIG. 8 (c) is a graph of field curvature and distortion of an optical imaging system; FIG. 8 (d) is a graph of diffraction efficiency at different wavelengths for a diffraction structure consisting of two diffractive microstructure facets in an optical imaging system; FIG. 8 (e) is an equivalent phase distribution of a first diffractive microstructure surface in an optical imaging system; FIG. 8 (f) is a microstructure distribution of a first diffractive microstructure surface in an optical imaging system; FIG. 8 (g) is an equivalent phase distribution of a second diffractive microstructure surface in an optical imaging system; fig. 8 (h) shows the microstructure distribution of the second diffractive microstructure surface in the optical imaging system.

In this embodiment, the optical imaging system shown in fig. 8 is applied to a super wide angle lens of a mobile phone, the focal length is 4.0mm, the relative caliber f# is 2.2, the total length of the optical system is 7.1mm, the detector is 1/2.3"cmos, and one free-form lens (the front and rear surfaces of the lens are polynomial free-form surfaces) and two microstructure diffraction surfaces are adopted. All the optical lens materials were resin materials, and the material distribution is shown in table 5 below:

TABLE 5

The second surface of the lens IV and the first surface of the lens V are diffraction microstructure surfaces, the interval between the two microstructure surfaces is 20 microns, and the microstructures of the two microstructure surfaces are distributed on an aspheric substrate. The microstructure height on the APL5014 material substrate was: h1 = 7.9839um; the microstructure height on the EP9000 material substrate is: h2 = 5.5917um. The front and rear surfaces of the lens six are free curved surfaces.

The microstructure surface phase coefficients are shown in table 6 below:

TABLE 6

Note that: the normalized radius corresponding to the phase coefficient is 100mm.

The diffractive microstructure substrate was aspherical and the corresponding aspherical coefficients are shown in table 7 below:

TABLE 7

The front and back surfaces of the sixth lens are free-form surfaces, and the free-form surface coefficients are shown in table 8 below:

TABLE 8

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Note that: the normalized radius is 2.052mm.

Example 3

As shown in fig. 9, which shows an optical imaging system having a full field FOV of between 30 ° and 90 °, the optical imaging system includes a lens 24, a lens 25, a lens 26, a lens 27, a lens 28, a lens 29, a lens 30, a lens 31, and an image detector 21, and a diaphragm is located between the lens 26 and the lens 27. Q1 to Q16 are all transmissive surfaces, wherein the second surface S2 of the lens 24, the first surface Q3 of the lens 25 are microstructured diffractive surfaces; the adjacent interval range of the two microstructure surfaces of Q2 and Q3 is 2-20 microns, and the two microstructure diffraction surfaces have the same substrate curved surface. The front and rear surfaces Q15 and Q16 of the lens 31 are free curved surfaces.

Fig. 9 (a) is an optical path diagram of an optical imaging system; FIG. 9 (b) is a graph of the modulation pass point function of the optical imaging system; FIG. 9 (c) is a graph of field curvature and distortion of an optical imaging system; FIG. 9 (d) is a graph of diffraction efficiency at different wavelengths for a diffraction structure consisting of two diffractive microstructure facets in an optical imaging system; FIG. 9 (e) is an equivalent phase distribution of a first diffractive microstructure surface in an optical imaging system; FIG. 9 (f) is a microstructure distribution of a first diffractive microstructure surface in an optical imaging system; FIG. 9 (g) is an equivalent phase distribution of a second diffractive microstructure surface in an optical imaging system; fig. 9 (h) shows the microstructure distribution of the second diffractive microstructure surface in the optical imaging system.

In this embodiment, the optical imaging system shown in fig. 8 is applied to the main lens of a mobile phone, the focal length is 8.65mm, the relative caliber f# is 1.72, the image plane diameter (diagonal line) is 16.2mm, and the total length of the optical system is 10.15mm. A free-form lens (the front and back surfaces of the lens are polynomial free-form surfaces) and two microstructured diffraction surfaces (as shown in fig. 9) are used. All the optical lens materials were resin materials, and the material distribution is shown in table 9 below:

TABLE 9

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The second surface of the first lens and the first surface of the second lens are diffraction microstructure surfaces, the interval between the two microstructure surfaces is 20 microns, and the microstructures of the two microstructure surfaces are distributed on an aspheric substrate. The microstructure height on the lens-substrate is: h1 = 6.894um; the microstructure height on the second substrate of the lens is as follows: h2 = 5.692um. Both the front and rear surfaces of the lens eight are free curved surfaces.

The microstructure surface phase coefficients are shown in table 10 below:

table 10

Sequence number	Phase coefficient	L1S2	L2S1
				1	A ₁	57.196	-111.560
2	A ₂	16.172	-1.120
				3	A ₃	-0.578	-2.176
4	A ₄	0.266	0.121
				5	A ₅	-0.011	-0.021
6	A ₆	0	0

The diffractive microstructure substrate is aspherical and the corresponding aspherical coefficients are shown in table 11 below:

TABLE 11

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The front and rear surfaces of the lens eight are free-form surfaces, and the free-form surface coefficients are shown in table 12 below:

table 12

Sequence number	High order coefficients	L8S1	L8S2
				1	b ₂₀	0.0067005051	0.026960233
2	b ₀₂	0.007809433	0.028802494
				3	b ₀₄	-0.03170201	-0.020051313
4	b ₂₂	-0.063531541	-0.040110896
				5	b ₄₀	-0.031319437	-0.019785553
6	b ₆₀	0.0047642861	0.0027600547
				7	b ₄₂	0.014484004	0.0082693794
8	b ₂₄	0.014482641	0.0082769294
				9	b ₀₆	0.0048222179	0.0027654127
10	...	...	...

Note that: the normalized radius is 1.0mm.

The foregoing embodiments have described in detail the technical solution and the advantages of the present invention, it should be understood that the foregoing embodiments are merely illustrative of the present invention and are not intended to limit the invention, and any modifications, additions and equivalents made within the scope of the principles of the present invention should be included in the scope of the invention.

Claims

1. An optical imaging system comprising a plurality of optical elements arranged along an optical path, wherein all surfaces of the plurality of optical elements comprise at least two of free-form surfaces, diffractive microstructure surfaces and super-surfaces; wherein when the diffraction microstructure faces are included, the diffraction microstructure faces are arranged in pairs.

2. The optical imaging system of claim 1, wherein the equation for the free-form surface is:

3. The optical imaging system of claim 2, wherein the free-form surface is of a double-symmetrical structure, polynomial E _i The odd-order term coefficients of x and y in (x, y) are 0, specifically as follows:

wherein A is _i Is a polynomial coefficient.

4. The optical imaging system of claim 1, wherein when a diffractive microstructured surface is included, two layers of diffractive microstructured surfaces of each pair are disposed on a planar, spherical, aspherical or freeform base of optical elements of different refractive index materials, the gap between the two layers of diffractive microstructured surfaces being air or another optically transmissive fill medium.

5. The optical imaging system of claim 4, wherein the spacing distance delta between the two diffraction microstructure surfaces is 1-20 um, and the phase distribution of the diffraction microstructure surfaces is respectively

And->

n _A (lambda) and n _B (lambda) is the refractive index of the two-material optical element; the heights of the two layers of diffraction microstructure surfaces are H respectively ₁ And H ₂ The phase height distribution function of the diffractive microstructure surface satisfies the following condition:

6. The optical imaging system according to claim 1, wherein the diffractive microstructure surface is a blazed binary optical microstructure, specifically: processing a ridged cylindrical diffraction microstructure optical surface with the size smaller than the micro nano size of wavelength on a substrate by adopting photoetching and etching processes, wherein the equivalent refractive index dispersion relation of the diffraction microstructure meets the following relation:

wherein d is the diameter of the microstructure cylinder or the width of the ridge; and satisfies f.lambda > δt, (1-f). Lambda > δt; wherein δt is the finest processed line width; equivalent refractive index is n _eff (f ₁ ,λ ₀ ) And n _eff (f ₂ ,λ ₀ ) I.e. the filling factor of the microstructure is between f ₁ And f ₂ Between them; the etching depth h satisfies:

phase transfer function

And->

The relation between the two is:

7. the optical imaging system of claim 1, wherein the supersurface is an artificial two-dimensional material having a nano-scale elliptic cylinder, cuboid or irregular pattern as a basic unit disposed on a planar or curved substrate, and comprises a transmissive or reflective supersurface.

8. An imaging lens, wherein the full field angle FOV of the imaging lens satisfies FOV >90 °, the optical imaging system of any one of claims 1 to 7 is employed, and the optical elements included in the optical imaging system are at least three lenses; all of the surfaces of the lens include at least one free-form surface and at least one pair of diffractive microstructured surfaces or a supersurface.

9. The imaging lens as claimed in claim 8, wherein the lens assembly of the optical imaging system from the object side to the image side along the optical axis comprises, in order: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens;

10. An imaging lens, wherein the full field angle FOV of the imaging lens satisfies FOV <30 °, and an optical imaging system according to any one of claims 1 to 7 is used, wherein the optical elements included in the optical imaging system are at least one lens and at least one prism including a refractive surface and a reflective surface, and the surfaces of all lenses include at least one free-form surface and at least one pair of diffraction microstructure surfaces or one super-surface.

11. The imaging lens as claimed in claim 10, wherein the optical imaging system includes a first lens, a second prism, and a third lens in order from an object side to an image side along an optical axis;

12. An imaging lens, characterized in that the full field angle FOV of the imaging lens satisfies 30 ° -90 ° or less, and the optical imaging system according to any one of claims 1 to 7 is adopted, and the optical elements included in the optical imaging system are at least four lenses; all of the lens surfaces include at least two free-form surfaces and at least one pair of diffractive microstructured surfaces or a supersurface.

13. The imaging lens as claimed in claim 12, wherein the optical imaging system includes, in order from an object side to an image side along an optical axis, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens;